# Copyright 2011 by Wibowo Arindrarto (w.arindrarto@gmail.com)
# Revisions copyright 2011-2016 by Peter Cock.
# This code is part of the Biopython distribution and governed by its
# license. Please see the LICENSE file that should have been included
# as part of this package.

"""Bio.SeqIO parser for the ABI format.

ABI is the format used by Applied Biosystem's sequencing machines to store
sequencing results.

For more details on the format specification, visit:
http://www.appliedbiosystem.com/support/software_community/ABIF_File_Format.pdf

"""


import datetime
import struct

from os.path import basename

from Bio import Alphabet
from Bio.Alphabet.IUPAC import ambiguous_dna, unambiguous_dna
from Bio.Seq import Seq
from Bio.SeqRecord import SeqRecord

from Bio._py3k import _bytes_to_string, _as_bytes
from Bio._py3k import zip

# dictionary for determining which tags goes into SeqRecord annotation
# each key is tag_name + tag_number
# if a tag entry needs to be added, just add its key and its key
# for the annotations dictionary as the value
# dictionary for tags that require preprocessing before use in creating
# seqrecords
_EXTRACT = {
    'TUBE1': 'sample_well',
    'DySN1': 'dye',
    'GTyp1': 'polymer',
    'MODL1': 'machine_model',
}


# Complete data structure representing 98% of the API. The general section
# represents the part of the API that's common to ALL instruments, whereas the
# instrument specific sections are labelled as they are in the ABIF spec
#
# Keys don't seem to clash from machine to machine, so when we parse, we look
# for ANY key, and store that in the raw ABIF data structure attached to the
# annotations, with the assumption that anyone parsing the data can look up the
# spec themself
#
# Key definitions are retained in case end users want "nice" labels pre-made
# for them for all of the available fields.
_INSTRUMENT_SPECIFIC_TAGS = {}

_INSTRUMENT_SPECIFIC_TAGS['general'] = {
    'APFN2': 'Sequencing Analysis parameters file name',
    'APXV1': 'Analysis Protocol XML schema version',
    'APrN1': 'Analysis Protocol settings name',
    'APrV1': 'Analysis Protocol settings version',
    'APrX1': 'Analysis Protocol XML string',
    'CMNT1': 'Sample Comment',
    'CTID1': 'Container Identifier, a.k.a. plate barcode',
    'CTNM1': 'Container name, usually identical to CTID, but not necessarily so',
    'CTTL1': 'Comment Title',
    'CpEP1': 'Capillary type electrophoresis. 1 for a capillary based machine. 0 for a slab gel based machine.',
    'DATA1': 'Channel 1 raw data',
    'DATA2': 'Channel 2 raw data',
    'DATA3': 'Channel 3 raw data',
    'DATA4': 'Channel 4 raw data',
    'DATA5': 'Short Array holding measured volts/10 (EP voltage) during run',
    'DATA6': 'Short Array holding measured milliAmps trace (EP current) during run',
    'DATA7': 'Short Array holding measured milliWatts trace (Laser EP Power) during run',
    'DATA8': 'Short Array holding measured oven Temperature (polymer temperature) trace during run',
    'DATA9': 'Channel 9 processed data',
    'DATA10': 'Channel 10 processed data',
    'DATA11': 'Channel 11 processed data',
    'DATA12': 'Channel 12 processed data',
    # Prism 3100/3100-Avant may provide DATA105
    #          3130/3130-XL may provide DATA105
    # 3530/3530-XL may provide DATA105-199, 9-12, 205-299
    'DSam1': 'Downsampling factor',
    'DySN1': 'Dye set name',
    'Dye#1': 'Number of dyes',
    'DyeN1': 'Dye 1 name',
    'DyeN2': 'Dye 2 name',
    'DyeN3': 'Dye 3 name',
    'DyeN4': 'Dye 4 name',
    'DyeW1': 'Dye 1 wavelength',
    'DyeW2': 'Dye 2 wavelength',
    'DyeW3': 'Dye 3 wavelength',
    'DyeW4': 'Dye 4 wavelength',
    # 'DyeN5-N': 'Dye 5-N Name',
    # 'DyeW5-N': 'Dye 5-N Wavelength',
    'EPVt1': 'Electrophoresis voltage setting (volts)',
    'EVNT1': 'Start Run event',
    'EVNT2': 'Stop Run event',
    'EVNT3': 'Start Collection event',
    'EVNT4': 'Stop Collection event',
    'FWO_1': 'Base Order. Sequencing Analysis Filter wheel order. Fixed for 3500 at "GATC"',
    'GTyp1': 'Gel or polymer Type',
    'InSc1': 'Injection time (seconds)',
    'InVt1': 'Injection voltage (volts)',
    'LANE1': 'Lane/Capillary',
    'LIMS1': 'Sample tracking ID',
    'LNTD1': 'Length to detector',
    'LsrP1': 'Laser Power setting (micro Watts)',
    'MCHN1': 'Instrument name and serial number',
    'MODF1': 'Data collection module file',
    'MODL1': 'Model number',
    'NAVG1': 'Pixels averaged per lane',
    'NLNE1': 'Number of capillaries',
    'OfSc1': 'List of scans that are marked off scale in Collection. (optional)',
    # OvrI and OrvV are listed as "1-N", and "One for each dye (unanalyzed
    # and/or analyzed data)"
    'OvrI1': 'List of scan number indexes that have values greater than 32767 but did not '
             'saturate the camera. In Genemapper samples, this can have indexes with '
             'values greater than 32000. In sequencing samples, this cannot have '
             'indexes with values greater than 32000.',
    'OvrI2': 'List of scan number indexes that have values greater than 32767 but did not '
             'saturate the camera. In Genemapper samples, this can have indexes with '
             'values greater than 32000. In sequencing samples, this cannot have '
             'indexes with values greater than 32000.',
    'OvrI3': 'List of scan number indexes that have values greater than 32767 but did not '
             'saturate the camera. In Genemapper samples, this can have indexes with '
             'values greater than 32000. In sequencing samples, this cannot have '
             'indexes with values greater than 32000.',
    'OvrI4': 'List of scan number indexes that have values greater than 32767 but did not '
             'saturate the camera. In Genemapper samples, this can have indexes with '
             'values greater than 32000. In sequencing samples, this cannot have '
             'indexes with values greater than 32000.',
    'OvrV1': 'List of color data values found at the locations listed in the OvrI tag. '
             'There must be exactly as many numbers in this array as in the OvrI array.',
    'OvrV2': 'List of color data values found at the locations listed in the OvrI tag. '
             'There must be exactly as many numbers in this array as in the OvrI array.',
    'OvrV3': 'List of color data values found at the locations listed in the OvrI tag. '
             'There must be exactly as many numbers in this array as in the OvrI array.',
    'OvrV4': 'List of color data values found at the locations listed in the OvrI tag. '
             'There must be exactly as many numbers in this array as in the OvrI array.',
    'PDMF1': 'Sequencing Analysis Mobility file name chosen in collection',
    'RMXV1': 'Run Module XML schema version',
    'RMdN1': 'Run Module name (same as MODF)',
    'RMdX1': 'Run Module XML string',
    'RPrN1': 'Run Protocol name',
    'RPrV1': 'Run Protocol version',
    'RUND1': 'Run Started Date',
    'RUND2': 'Run Stopped Date',
    'RUND3': 'Data Collection Started Date',
    'RUND4': 'Data Collection Stopped date',
    'RUNT1': 'Run Started Time',
    'RUNT2': 'Run Stopped Time',
    'RUNT3': 'Data Collection Started Time',
    'RUNT4': 'Data Collection Stopped Time',
    'Rate1': 'Scanning Rate. Milliseconds per frame.',
    'RunN1': 'Run Name',
    'SCAN1': 'Number of scans',
    'SMED1': 'Polymer lot expiration date',
    'SMLt1': 'Polymer lot number',
    'SMPL1': 'Sample name',
    'SVER1': 'Data collection software version',
    'SVER3': 'Data collection firmware version',
    'Satd1': 'Array of longs representing the scan numbers of data points, which are flagged as saturated by data collection (optional)',
    'Scal1': 'Rescaling divisor for color data',
    'Scan1': 'Number of scans (legacy - use SCAN)',
    'TUBE1': 'Well ID',
    'Tmpr1': 'Run temperature setting',
    'User1': 'Name of user who created the plate (optional)',
}

#  No instrument specific tags
# _INSTRUMENT_SPECIFIC_TAGS['abi_prism_3100/3100-Avant'] = {
# }

_INSTRUMENT_SPECIFIC_TAGS['abi_3130/3130xl'] = {
    'CTOw1': 'Container owner',
    'HCFG1': 'Instrument Class',
    'HCFG2': 'Instrument Family',
    'HCFG3': 'Official Instrument Name',
    'HCFG4': 'Instrument Parameters',
    'RMdVa1': 'Run Module version',
}

_INSTRUMENT_SPECIFIC_TAGS['abi_3530/3530xl'] = {
    'AAct1': 'Primary Analysis Audit Active indication. True if system auditing was enabled during the last write of this file, '
             'false if system auditing was disabled.',
    'ABED1': 'Anode buffer expiration date using ISO 8601 format using the patterns YYYY-MM-DDTHH:MM:SS.ss+/-HH:MM. Hundredths of a second are optional.',
    'ABID1': 'Anode buffer tray first installed date',
    'ABLt1': 'Anode buffer lot number',
    'ABRn1': 'Number of runs (injections) processed with the current Anode Buffer (runs allowed - runs remaining)',
    'ABTp1': 'Anode buffer type',
    'AEPt1': 'Analysis Ending scan number for basecalling on initial analysis',
    'AEPt2': 'Analysis Ending scan number for basecalling on last analysis',
    'APCN1': 'Amplicon name',
    'ARTN1': 'Analysis Return code. Produced only by 5 Prime basecaller 1.0b3',
    'ASPF1': 'Flag to indicate whether adaptive processing worked or not',
    'ASPt1': 'Analysis Starting scan number for first analysis',
    'ASPt2': 'Analysis Starting scan number for last analysis',
    'AUDT2': 'Audit log used across 3500 software (optional)',
    'AVld1': 'Assay validation flag (true or false)',
    'AmbT1': 'Record of ambient temperature readings',
    'AsyC1': 'The assay contents (xml format)',
    'AsyN1': 'The assay name',
    'AsyV1': 'The assay version',
    'B1Pt1': 'Reference scan number for mobility and spacing curves for first analysis',
    'B1Pt2': 'Reference scan number for mobility and spacing curves for last analysis',
    'BCTS1': 'Basecaller timestamp. Time of completion of most recent analysis',
    'BcRn1': 'Basecalling qc code',
    'BcRs1': 'Basecalling warnings, a concatenated comma separated string',
    'BcRs2': 'Basecalling errors, a concatenated comma separated string',
    'CAED1': 'Capillary array expiration',
    'CALt1': 'Capillary array lot number',
    'CARn1': 'Number of injections processed (including the one of which this sample was a part) through the capillary array',
    'CASN1': 'Capillary array serial number',
    'CBED1': 'Cathode buffer expiration date',
    'CBID1': 'Cathode buffer tray first installed date',
    'CBLt1': 'Cathode buffer lot number',
    'CBRn1': 'Number of runs (injections) processed with the current Cathode Buffer (runs allowed - runs remaining)',
    'CBTp1': 'Cathode buffer type',
    'CLRG1': 'Start of the clear range (inclusive).',
    'CLRG2': 'Clear range length',
    'CRLn1': 'Contiguous read length',
    'CRLn2': 'One of "Pass", "Fail", or "Check"',
    'CTOw1': 'The name entered as the Owner of a plate, in the plate editor',
    'CkSm1': 'File checksum',
    'DCEv1': 'A list of door-close events, separated by semicolon. Door open events are generally paired with door close events.',
    'DCHT1': 'Reserved for backward compatibility. The detection cell heater temperature setting from the Run Module. Not used for 3500.',
    'DOEv1': 'A list of door-open events, separated by semicolon. Door close events are generally paired with door open events.',
    'ESig2': 'Electronic signature record used across 3500 software',
    'FTab1': 'Feature table. Can be created by Nibbler for Clear Range.',
    'FVoc1': 'Feature table vocabulary. Can be created by Nibbler for Clear Range.',
    'Feat1': 'Features. Can be created by Nibbler for Clear Range.',
    'HCFG1': 'The Instrument Class. All upper case, no spaces. Initial valid value: CE',
    'HCFG2': 'The Instrument Family. All upper case, no spaces. Valid values: 31XX or 37XX for UDC, 35XX (for 3500)',
    'HCFG3': 'The official instrument name. Mixed case, minus any special formatting. Initial valid values: 3130, 3130xl, 3730, 3730xl, 3500, 3500xl.',
    'HCFG4': 'Instrument parameters. Contains key-value pairs of instrument configuration information, separated by semicolons. '
             'Four parameters are included initially: UnitID=<UNITD number>, CPUBoard=<board type>, '
             'ArraySize=<# of capillaries>, SerialNumber=<Instrument Serial#>.',
    'InjN1': 'Injection name',
    'LAST1': 'Parameter settings information',
    'NOIS1': 'The estimate of rms baseline noise (S/N ratio) for each dye for a successfully analyzed sample. '
             'Corresponds in order to the raw data in tags DATA 1-4. KB basecaller only.',
    'P1AM1': 'Amplitude of primary peak, which is not necessarily equal to corresponding signal strength at that position',
    'P1RL1': 'Deviation of primary peak position from (PLoc,2), times 100, rounded to integer',
    'P1WD1': 'Full-width Half-max of primary peak, times 100, rounded to integer. '
             'Corresponding signal intensity is not necessarily equal to one half of primary peak amplitude',
    'P2AM1': 'Amplitude of secondary peak, which is not necessarily equal to corresponding signal strength at that position',
    'P2BA1': 'Base of secondary peak',
    'P2RL1': 'Deviation of secondary peak position from (PLoc,2), times 100, rounded to integer',
    'PBAS1': 'Array of sequence characters edited by user',
    'PBAS2': 'Array of sequence characters as called by Basecaller',
    'PCON1': 'Array of quality Values (0-255) as edited by user',
    'PCON2': 'Array of quality values (0-255) as called by Basecaller',
    'PDMF2': 'Mobility file name chosen in most recent analysis (identical to PDMF1)',
    'PLOC1': 'Array of peak locations edited by user',
    'PLOC2': 'Array of peak locations as called by Basecaller',
    'PRJT1': 'SeqScape 2.0 project template name',
    'PROJ4': 'SeqScape 2.0 project name',
    'PSZE1': 'Plate size. The number of sample positions in the container. Current allowed values: 96, 384.',
    'PTYP1': 'Plate type. Current allowed values: 96-Well, 384-Well.',
    'PuSc1': 'Median pupscore',
    'QV201': 'QV20+ value',
    'QV202': 'One of "Pass", "Fail", or "Check"',
    'QcPa1': 'QC parameters',
    'QcRn1': 'Trimming and QC code',
    'QcRs1': 'QC warnings, a concatenated comma separated string',
    'QcRs2': 'QC errors, a concatenated comma separated string',
    'RGOw1': 'The name entered as the Owner of a Results Group, in the Results Group Editor. Implemented as the user name from the results group.',
    'RInj1': 'Reinjection number. The reinjection number that this sample belongs to. Not present if there was no reinjection.',
    'RNmF1': 'Raman normalization factor',
    'RevC1': 'for whether the sequence has been complemented',
    'RunN1': 'Run name (which, for 3500, is different from injection name)',
    'S/N%1': 'Signal strength for each dye',
    'SMID1': 'Polymer first installed date',
    'SMRn1': 'Number of runs (injections) processed with the current polymer (runs allowed - runs remaining)',
    'SPAC1': 'Average peak spacing used in last analysis',
    'SPAC2': 'Basecaller name - corresponds to name of bcp file.',
    'SPAC3': 'Average peak spacing last calculated by the Basecaller.',
    'SPEC1': 'Sequencing Analysis Specimen Name',
    'SVER2': 'Basecaller version number',
    'SVER4': 'Sample File Format Version String',
    'ScPa1': 'The parameter string of size caller',
    'ScSt1': 'Raw data start point. Set to 0 for 3500 data collection.',
    'SpeN1': 'Active spectral calibration name',
    'TrPa1': 'Timming parameters',
    'TrSc1': 'Trace score.',
    'TrSc2': 'One of "Pass", "Fail", or "Check"',
    'phAR1': 'Trace peak aria ratio',
    'phCH1': 'Chemistry type ("term", "prim", "unknown"), based on DYE_1 information',
    'phDY1': 'Dye ("big", "d-rhod", "unknown"), based on mob file information',
    'phQL1': 'Maximum Quality Value',
    'phTR1': 'Set Trim region',
    'phTR2': 'Trim probability',
}

_INSTRUMENT_SPECIFIC_TAGS['abi_3730/3730xl'] = {
    'BufT1': 'Buffer tray heater temperature (degrees C)',
}

# dictionary for data unpacking format
_BYTEFMT = {
    1: 'b',     # byte
    2: 's',     # char
    3: 'H',     # word
    4: 'h',     # short
    5: 'i',     # long
    6: '2i',    # rational, legacy unsupported
    7: 'f',     # float
    8: 'd',     # double
    10: 'h2B',  # date
    11: '4B',   # time
    12: '2i2b',  # thumb
    13: 'B',    # bool
    14: '2h',   # point, legacy unsupported
    15: '4h',   # rect, legacy unsupported
    16: '2i',   # vPoint, legacy unsupported
    17: '4i',   # vRect, legacy unsupported
    18: 's',    # pString
    19: 's',    # cString
    20: '2i',   # tag, legacy unsupported
}
# header data structure (exluding 4 byte ABIF marker)
_HEADFMT = '>H4sI2H3I'
# directory data structure
_DIRFMT = '>4sI2H4I'

__global_tag_listing = []
for tag in _INSTRUMENT_SPECIFIC_TAGS.values():
    __global_tag_listing += tag.keys()


def AbiIterator(handle, alphabet=None, trim=False):
    """Iterator for the Abi file format.
    """
    # raise exception is alphabet is not dna
    if alphabet is not None:
        if isinstance(Alphabet._get_base_alphabet(alphabet),
                      Alphabet.ProteinAlphabet):
            raise ValueError(
                "Invalid alphabet, ABI files do not hold proteins.")
        if isinstance(Alphabet._get_base_alphabet(alphabet),
                      Alphabet.RNAAlphabet):
            raise ValueError("Invalid alphabet, ABI files do not hold RNA.")

    # raise exception if handle mode is not 'rb'
    if hasattr(handle, 'mode'):
        if set('rb') != set(handle.mode.lower()):
            raise ValueError("ABI files has to be opened in 'rb' mode.")

    # check if input file is a valid Abi file
    handle.seek(0)
    marker = handle.read(4)
    if not marker:
        # handle empty file gracefully
        raise StopIteration
    if marker != _as_bytes('ABIF'):
        raise IOError('File should start ABIF, not %r' % marker)

    # dirty hack for handling time information
    times = {'RUND1': '', 'RUND2': '', 'RUNT1': '', 'RUNT2': '', }

    # initialize annotations
    annot = dict(zip(_EXTRACT.values(), [None] * len(_EXTRACT)))

    # parse header and extract data from directories
    header = struct.unpack(_HEADFMT,
                           handle.read(struct.calcsize(_HEADFMT)))

    raw = dict()
    for tag_name, tag_number, tag_data in _abi_parse_header(header, handle):
        key = tag_name + str(tag_number)

        raw[key] = tag_data

        # PBAS2 is base-called sequence, only available in 3530
        if key == 'PBAS2':
            seq = tag_data
            ambigs = 'KYWMRS'
            if alphabet is None:
                if set(seq).intersection(ambigs):
                    alphabet = ambiguous_dna
                else:
                    alphabet = unambiguous_dna
        # PCON2 is quality values of base-called sequence
        elif key == 'PCON2':
            qual = [ord(val) for val in tag_data]
        # SMPL1 is sample id entered before sequencing run
        elif key == 'SMPL1':
            sample_id = tag_data
        elif key in times:
            times[key] = tag_data
        else:
            if key in _EXTRACT:
                annot[_EXTRACT[key]] = tag_data

    # set time annotations
    annot['run_start'] = '%s %s' % (times['RUND1'], times['RUNT1'])
    annot['run_finish'] = '%s %s' % (times['RUND2'], times['RUNT2'])

    # raw data (for advanced end users benefit)
    annot['abif_raw'] = raw

    # use the file name as SeqRecord.name if available
    try:
        file_name = basename(handle.name).replace('.ab1', '')
    except AttributeError:
        file_name = ""
    record = SeqRecord(Seq(seq, alphabet),
                       id=sample_id, name=file_name,
                       description='',
                       annotations=annot,
                       letter_annotations={'phred_quality': qual})

    if not trim:
        yield record
    else:
        yield _abi_trim(record)


def _AbiTrimIterator(handle):
    """Iterator for the Abi file format that yields trimmed SeqRecord objects.
    """
    return AbiIterator(handle, trim=True)


def _abi_parse_header(header, handle):
    """Generator that returns directory contents.
    """
    # header structure (after ABIF marker):
    # file version, tag name, tag number,
    # element type code, element size, number of elements
    # data size, data offset, handle (not file handle)
    head_elem_size = header[4]
    head_elem_num = header[5]
    head_offset = header[7]
    index = 0

    while index < head_elem_num:
        start = head_offset + index * head_elem_size
        # add directory offset to tuple
        # to handle directories with data size <= 4 bytes
        handle.seek(start)
        dir_entry = struct.unpack(_DIRFMT,
                                  handle.read(struct.calcsize(_DIRFMT))) + (start,)
        index += 1
        # only parse desired dirs
        key = _bytes_to_string(dir_entry[0])
        key += str(dir_entry[1])

        tag_name = _bytes_to_string(dir_entry[0])
        tag_number = dir_entry[1]
        elem_code = dir_entry[2]
        elem_num = dir_entry[4]
        data_size = dir_entry[5]
        data_offset = dir_entry[6]
        tag_offset = dir_entry[8]
        # if data size <= 4 bytes, data is stored inside tag
        # so offset needs to be changed
        if data_size <= 4:
            data_offset = tag_offset + 20
        handle.seek(data_offset)
        data = handle.read(data_size)
        yield tag_name, tag_number, \
            _parse_tag_data(elem_code, elem_num, data)


def _abi_trim(seq_record):
    """Trims the sequence using Richard Mott's modified trimming algorithm.

    Arguments:
        - seq_record - SeqRecord object to be trimmed.

    Trimmed bases are determined from their segment score, which is a
    cumulative sum of each base's score. Base scores are calculated from
    their quality values.

    More about the trimming algorithm:
    http://www.phrap.org/phredphrap/phred.html
    http://www.clcbio.com/manual/genomics/Quality_abif_trimming.html
    """

    start = False   # flag for starting position of trimmed sequence
    segment = 20    # minimum sequence length
    trim_start = 0  # init start index
    cutoff = 0.05   # default cutoff value for calculating base score

    if len(seq_record) <= segment:
        return seq_record
    else:
        # calculate base score
        score_list = [cutoff - (10 ** (qual / -10.0)) for qual in
                      seq_record.letter_annotations['phred_quality']]

        # calculate cummulative score
        # if cummulative value < 0, set it to 0
        # first value is set to 0, because of the assumption that
        # the first base will always be trimmed out
        cummul_score = [0]
        for i in range(1, len(score_list)):
            score = cummul_score[-1] + score_list[i]
            if score < 0:
                cummul_score.append(0)
            else:
                cummul_score.append(score)
                if not start:
                    # trim_start = value when cummulative score is first > 0
                    trim_start = i
                    start = True

        # trim_finish = index of highest cummulative score,
        # marking the end of sequence segment with highest cummulative score
        trim_finish = cummul_score.index(max(cummul_score))

        return seq_record[trim_start:trim_finish]


def _parse_tag_data(elem_code, elem_num, raw_data):
    """Returns single data value.

    Arguments:
        - elem_code - What kind of data
        - elem_num - How many data points
        - raw_data - abi file object from which the tags would be unpacked
    """
    if elem_code in _BYTEFMT:
        # because '>1s' unpack differently from '>s'
        if elem_num == 1:
            num = ''
        else:
            num = str(elem_num)
        fmt = '>' + num + _BYTEFMT[elem_code]

        assert len(raw_data) == struct.calcsize(fmt)
        data = struct.unpack(fmt, raw_data)

        # no need to use tuple if len(data) == 1
        # also if data is date / time
        if elem_code not in [10, 11] and len(data) == 1:
            data = data[0]

        # account for different data types
        if elem_code == 2:
            return _bytes_to_string(data)
        elif elem_code == 10:
            return str(datetime.date(*data))
        elif elem_code == 11:
            return str(datetime.time(*data[:3]))
        elif elem_code == 13:
            return bool(data)
        elif elem_code == 18:
            return _bytes_to_string(data[1:])
        elif elem_code == 19:
            return _bytes_to_string(data[:-1])
        else:
            return data
    else:
        return None

if __name__ == '__main__':
    pass
